As the worldwide demand for oil and gas has continued to escalate, the systems used to control and monitor the production of oil and gas wells have continued to increase in sophistication and complexity. It is not uncommon for wells to have a significant number of production zones, and to incorporate multiple sets of monitoring and control systems, each requiring separate sets of communication and control lines between the surface and the downhole equipment located within each production zone. Such communication and control lines may include hydraulic lines, copper electrical lines, and optical fiber lines, just to name a few examples. While techniques do exist for attaching multiple lines to production tubing as they are introduced into the well during the well completion process, the use of expansion joints along the length of the production tubing may limit or even preclude the use of multiple lines.
Expansion joints are necessary in extreme environments that subject the production tubing to significant expansion and compression forces such as those found, for example, in offshore wells or in deep wells where the production tubing can be subjected to large variations in temperature both in the surrounding strata and in the product being extracted through the tubing. These temperature variations over very large lengths of production tubing can produce significant variations in tubing length, thus necessitating the use of expansion joints over the length of the production tubing to relieve the stresses created and to avoid damaging the tubing and any production equipment coupled to the tubing.
Existing systems using a single control/communication line, such as a ¼″ hydraulic control line attached to the outside of the production tubing from the surface to the downhole equipment being controlled (e.g., a downhole safety valve), are sometimes configured to account for the variations in tubing length at the expansion joint by coiling the control line around the joint, thus allowing the line to coil and uncoil as the joint correspondingly contracts and extends. While it is possible to incorporate such line coils around expansion joints when using a single control/communication line, such coiling may not work with systems that require even as few as two or three lines. This is due to the fact that over time, as the joint contracts and extends, the control/communication lines will tend to become entangled, which over time can damage the lines. If the lines are damaged, it may become necessary to shut the well down and set up a “workover” rig to remove the production tubing and replace the damaged lines. Such repairs are extremely expensive, both in terms of the direct costs of performing the repairs, as well as in terms of lost production due to the significant amount of time it takes to perform the repairs.